Extracellular vesicles (EVs) are lipid bilayered compartments released by virtually all living cells, including fungi. Among the diverse molecules carried by fungal EVs, a number of immunogens, virulence factors and regulators have been characterised. Within EVs, these components could potentially impact disease outcomes by interacting with the host. From this perspective, we previously demonstrated that EVs from Candida albicans could be taken up by and activate macrophages and dendritic cells to produce cytokines and express costimulatory molecules. Moreover, pre‐treatment of Galleria mellonella larvae with fungal EVs protected the insects against a subsequent lethal infection with C. albicans yeasts. These data indicate that C. albicans EVs are multi‐antigenic compartments that activate the innate immune system and could be exploited as vaccine formulations. Here, we investigated whether immunisation with C. albicans EVs induces a protective effect against murine candidiasis in immunosuppressed mice. Total and fungal antigen‐specific serum IgG antibodies increased by 21 days after immunisation, confirming the efficacy of the protocol. Vaccination decreased fungal burden in the liver, spleen and kidney of mice challenged with C. albicans. Splenic levels of cytokines indicated a lower inflammatory response in mice immunised with EVs when compared with EVs + Freund's adjuvant (ADJ). Higher levels of IL‐12p70, TNFα and IFNγ were detected in mice vaccinated with EVs + ADJ, while IL‐12p70, TGFβ, IL‐4 and IL‐10 were increased when no adjuvants were added. Full protection of lethally challenged mice was observed when EVs were administered, regardless the presence of adjuvant. Physical properties of the EVs were also investigated and EVs produced by C. albicans were relatively stable after storage at 4, −20 or −80°C, keeping their ability to activate dendritic cells and to protect G. mellonella against a lethal candidiasis. Our data suggest that fungal EVs could be a safe source of antigens to be exploited in vaccine formulations.

中文翻译：

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真菌细胞外囊泡对鼠念珠菌病的保护作用。

细胞外囊泡 (EV) 是由几乎所有活细胞（包括真菌）释放的脂质双层隔室。在真菌 EV 携带的各种分子中，已经表征了许多免疫原、毒力因子和调节剂。在 EV 中，这些成分可能通过与宿主相互作用而影响疾病结果。从这个角度来看，我们之前已经证明来自白色念珠菌的EV可以被巨噬细胞和树突细胞吸收并激活，以产生细胞因子和表达共刺激分子。此外，用真菌 EV预处理大蜡螟幼虫可以保护昆虫免受随后的白色念珠菌酵母菌的致命感染。这些数据表明白色念珠菌EVs 是激活先天免疫系统的多抗原隔室，可用作疫苗制剂。在这里，我们研究了白色念珠菌EV免疫是否在免疫抑制小鼠中诱导对鼠念珠菌病的保护作用。免疫接种后 21 天，总抗体和真菌抗原特异性血清 IgG 抗体增加，证实了该方案的有效性。接种疫苗降低了感染白色念珠菌的小鼠肝脏、脾脏和肾脏中的真菌负担. 与 EVs + 弗氏佐剂 (ADJ) 相比，脾脏细胞因子水平表明，用 EVs 免疫的小鼠炎症反应较低。在接种 EVs + ADJ 的小鼠中检测到更高水平的 IL-12p70、TNFα 和 IFNγ，而当不添加佐剂时，IL-12p70、TGFβ、IL-4 和 IL-10 增加。无论佐剂是否存在，当给予 EVs 时，都观察到了对致命攻击小鼠的完全保护。还研究了 EV 的物理特性，白色念珠菌产生的 EV在 4、-20 或 -80°C 下储存后相对稳定，保持其激活树突状细胞和保护大蜡螟的能力对抗致命的念珠菌病。我们的数据表明，真菌 EV 可能是可用于疫苗制剂的安全抗原来源。